Largest Safe Water Change For 29G Nano?

[old_salt]

What is the largest water change you would recommend for a 29 Gallon Bio Cube? I need to transfer about 14 gallons to a newly established seahorse tank and I'm concerned this might upset the balance of the 29G tank. I do have bio balls, bio filter and about 20 pounds of live rock in this tank and it has been up and running for about 6 months. The reason I prefer this water instead of fresh saltwater is that the babies were born in this tank on Saturday. Any help would be appreciated. Thanks!
https://forums.saltwaterfish.com/t/290326/one-of-my-horses-just-had-babies

 

[codyjp]

I have done 10 gallons in my 24 many times with no problems. You could do that and then a few hours later do another 5 gallons... That would get things mixed up slowly.

 

[old_salt]

Originally Posted by codyjp
I have done 10 gallons in my 24 many times with no problems. You could do that and then a few hours later do another 5 gallons... That would get things mixed up slowly.
I will do this tomorrow. I moved another 4 gallons tonight and will take the rest tomorrow morning. I still need at least 7 gallons for the main tank and 4 for the sump. So far all occupants in both tanks seem to be doing okay. Thanks again!